We introduce a marriage and family therapy (MFT) concept called we-ness to help improve new product development (NPD) performance by focusing on relationships between team members. In this chapter, we (1) describe the concept of we-ness,(2) explain the relationship between we-ness and knowledge sharing in NPD teams and its effect on product performance,(3) present a model that explains how more knowledge sharing occurs when we-ness-enhancing actions are taken and how it increases product performance, and (4) suggest how NPD organizations can create more family-like and productive environments. We-ness is commonly associated within the relational dynamics among immediate family members (Reid, Dalton, Laderoute, Doell, and Nguyen, 2007; Seider, Hieschberger, Nelson, and Levenson, 2009). It is important in social environments because the formation of close relationships involves a partial transformation of the self—a shift from being separate individuals to being joined with others (Reid et al., 2007; Seider et al., 2009). We-ness will help product development managers foster a more productive environment among team members and even between teams inside and outside the organization.